feat: create acceptance tests for tx pool feature

[natanasow]

Description

Create acceptance tests for the feature based on the Acceptance Criteria created when designing the feature.

Related issue(s)

Fixes #4396

Testing Guide

Changes from original design (optional)

N/A

Additional work needed (optional)

N/A

Checklist

• I've assigned an assignee to this PR and related issue(s) (if applicable)
• I've assigned a label to this PR and related issue(s) (if applicable)
• I've assigned a milestone to this PR and related issue(s) (if applicable)
• I've updated documentation (code comments, README, etc. if applicable)
• I've done sufficient testing (unit, integration, etc.)

[github-actions]

Test Results

 20 files  ±0  263 suites   - 2   18m 30s ⏱️ - 32m 45s
760 tests  - 2  751 ✅  - 1  5 💤 ±0  4 ❌  - 1 
780 runs  +2  771 ✅ +3  5 💤 ±0  4 ❌  - 1 

For more details on these failures, see this check.

Results for commit 6cbc389. ± Comparison against base commit 57c9fa1.

♻️ This comment has been updated with latest results.

[konstantinabl]

few comments and questions

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@                    Coverage Diff                    @@
##           feat/transaction-pool    #4443      +/-   ##
=========================================================
+ Coverage                  94.78%   95.87%   +1.09%     
=========================================================
  Files                        126      126              
  Lines                      20315    20311       -4     
  Branches                    1688     1762      +74     
=========================================================
+ Hits                       19255    19473     +218     
+ Misses                      1035      814     -221     
+ Partials                      25       24       -1     

Flag	Coverage Δ
config-service	98.81% <ø> (ø)
relay	90.93% <92.85%> (-0.01%)	⬇️
server	88.82% <ø> (?)
ws-server	98.27% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
packages/relay/src/lib/eth.ts	99.49% <100.00%> (+<0.01%)	⬆️
packages/relay/src/lib/precheck.ts	98.73% <100.00%> (ø)
...thService/transactionService/TransactionService.ts	97.47% <100.00%> (-0.30%)	⬇️
...s/transactionPoolService/transactionPoolService.ts	100.00% <ø> (ø)

... and 11 files with indirect coverage changes

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